This invention relates to a multi-color mechanical writing instrument operated by push action by one hand. Various types of conventional multi-color mechanical writing instruments have been developed. For instance, a conventional multi-color mechanical writing instrument incorporates a plural number of ink tubes or reservoirs arranged in parallel in the casing, and the push-bar placed on top of the respective color ink tubes rotates to have the push-bar positioned on a selected ink tube. When selected for writing, the push-bar is depressed to push a selected color tip out. This conventional type of writing instrument requires an operation to rotate the push-bar or twist a selected color ink tube by using both hands so as to be inconvenient.
Another conventional type of a writing instrument incorporates a plural number of color indentification push-buttons around the outer surface of the casing to push the selected color tip out or pull it back by a pushing operation of the respective color identification button desired, which require additional operations to identify the color desired and set it properly to push the selected tip out by both hands.